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A physicist and citizen scientists collaborated and discovered a new type of aurora borealis, which they've dubbed the 'dunes.'
The new aurora seems to be caused by mesospheric bores which could be a result of Joule heating.
Further analysis will be needed to reach a more definitive conclusion.
In early October 2018, Minna Palmroth, a Finnish physicist and professor of computational space physics with the University of Helsinki, was wrapping a guidebook called A Guide for Aurora Borealis Watchers when she—along with some Facebook citizen scientists—discovered something unexpected.
"Maybe we need to make a new category," Palmroth said in an interview with Gizmodo, "because they didn't seem like anything I had seen before."
Palmroth, and her Facebook team of Aurora enthusiasts, had spotted a previously unclassified aurora borealis. The team would name the discovery, "the dunes," a description of the phenomenon's undulating auroral mounds. Palmroth describes the dunes in a new paper published in AGU Advances.
— Minna Palmroth (@MinnaPalmroth) January 29, 2020
The dunes difference other auroras is in its shape. Dune auroras produce a wave-like pattern across the sky and, like other auroras, are the result of charged solar particles coming into contact with Earth's atmosphere.
The waves are likely a product of mesospheric bores, which are typically the result of airflow that gets stuck and contorted in between the layers of the Earth's atmosphere. When solar wind hits a mesospheric bore, the bore becomes visible as particles from the sun slam into the Earth's atmosphere, charging the molecules there and lighting them up.
To be sure of their discovery, Palmroth and the group of amateur stargazers needed more information. A few days later, on October 7, 2018, the northern lights put on a dazzling show over Finland—in the dune formation.
Several stargazers in different locations across the Finland and Sweden were able to capture footage of the atmospheric event. This data helped Palmroth pinpoint the aurora's location by using the surrounding stars as a guide. They discovered that the dunes aurora occurred in two places, 107 miles apart and 60 miles in the mesosphere, Earth's coldest atmosphere, sandwiched between the stratosphere and thermosphere.
The American Geophysical Union says that the dunes are a product of their environment and are "visible manifestations of undulations of air called atmospheric waves." These waves are caused by mesospheric bores.
Additionally, Palmroth and team have found that the dunes happen at the same time and in the same area where the Earth's upper atmosphere absorbs electromagnetic energy. This movement of energy led Palmroth to believe that Joule heating—the creation of heat resulting from an electric current passing through a conductor—could create an environment conducive to bore production.
Palmroth and these citizen scientists have already broken ground on dune aurora research and are hoping that additional analysis will unlock more information about the mysterious mesosphere.
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